The present invention relates to a sewing machine, and more particularly, a bobbin case of a rotary shuttle device for a sewing machine, which continuously and stably guides and supplies an under thread pulled out of bobbin to a sewing region.
Generally, an embroidery, domestic or industrial sewing machine, as shown in FIG. 1, has a rotary shuttle device for supplying an under thread. The rotary shuttle device comprises an outer shuttle which is disposed at a driving shaft 1 rotatably connected to a power generating unit, an inner shuttle 3 which is received in the outer shuttle 2, a bobbin 4 which is received in the inner shuttle 3 and on which the under thread is wound, and a bobbin case 5 for receiving the bobbin 4. Recently, in order to wind a large amount of the under thread on the bobbin 4, the bobbin 4 is provided with sidewalls 4a, 4b respectively formed at both ends thereof and a partition wall 4c formed between the sidewalls 4a, 4b to have a trough portion. According to a construction of the rotary shuttle device as described above, when performing a sewing operation, the outer and inner shuttles 2, 3 are relatively rotated, and at the same time, the under thread wound on the bobbin 4 is pulled out and supplied through the bobbin case 5 and the outer shuttle 2 to a lower portion of cloth to be sewn. Then, the under thread is sewn into the cloth in cooperation with an upper thread supplied from an upper portion of the cloth. At this time, the bobbin case 5 guides the under thread pulled out of the bobbin 4 to the outer shuttle 3 or a sewing region.
As shown in FIG. 2, the bobbin case 5 is comprised of a main body 7 having a discharging hole 6 for discharging the under thread pulled out of the bobbin 4, and a guide member 8 which is formed in the shape of a leaf spring type to guide the under thread discharged through the discharging hole 6 of the main body 7 and also prevent separation of the under thread. Meanwhile, the main body 7 is further formed with a circular through hole 7a, a rectangular supporting hole 7b, a fixing hole 7c and an adjusting hole 7d. Corresponding to the holes of the main body 7, at a front end side of the guide member 8, there are formed a first supporting piece 8a inserted into the through hole 7a of the main body 7 and a second supporting piece 8b inserted into the supporting hole 7b, and also at a rear end side of the guide member 8, there are formed a coupling hole 8c for fixing the guide member 8 to the main body 7 and a controlling hole 8d formed to be adjacent to the coupling hole 8c to adjust elastic force of the guide member 8. In addition, between the constructing portions as described above, there is formed a guide groove for guiding the under thread. Of course, a fastening bolt 9a is fastened through the coupling hole 8c into the fixing hole 7c. A controlling bolt 9b is also screwed into the controlling hole 8d. Then, the controlling bolt is tightened or loosened to properly control the elastic force of the guide member 8. In case the bobbin is used in the embroidery sewing machine, an outlet port may be formed at a proper place of the main body 7 so that the under thread can substantially get out of the main body 7. Further, at the discharging hole 6 of the main body 7 is formed a xe2x80x9cxe2x80x9d shaped groove 6a for guiding the under thread to the discharging hole 6.
According to the construction as described above, the under thread pulled out of the bobbin 4 goes out of the discharging hole 6 of the main body 7 and passes between a side portion of the main body 7 and the guide member 8, or is then supplied through the outlet port formed at the main body to the outer shuttle 2. At this time, the under thread substantially gets out of the outlet port (not shown) via a guide trough between the first supporting piece 8a and the second supporting piece 8b of the guide member 8.
However, the bobbin case constructed as above causes various problems as follows. First, since the under thread pulled out through the discharging hole 6 of the main body 7 is positioned within a range of the partition wall of the bobbin 4 which is rotated at a high speed in the main body 7, the under thread is damaged, and in the worst case, cut by the partition wall.
Secondly, since the guide trough formed among the constructing portions of the guide member has a wide guide region, a moving and fluctuating extent of the under thread is increased. Therefore, there is a problem that the under thread is not precisely and stably supplied to the outlet portion of the main body.
Thirdly, the under thread pulled out of the bobbin 4 cannot maintains proper tensile force due to the above problems. Further, intermittent phenomenon and intermittent sound are generated when supplying the under thread, thereby lowering the quantity of sewn products and also reducing stillness in an operation of the sewing machine.
Additionally, a groove for inserting the under thread into the discharging hole is curved. Therefore, there is other problem that it is difficult to insert the under thread into the discharging hole.
Therefore, it is an object of the present invention to provide a bobbin case of a rotary shuttle device for a sewing machine, which is capable of preventing damage or cut of a under thread passing through a main body from a bobbin.
It is other object of the present invention to provide a bobbin case of a rotary shuttle device for a sewing machine, which is capable of deviating the under thread passing through a discharging hole of the main body from the range of a partition wall of a bobbin rotated in the main body.
It is another object of the present invention to provide a bobbin case of a rotary shuttle device for a sewing machine, by which the under thread is pulled out of a bobbin through an optical region of a guide member, while maintaining optical tensile force.
It is yet another object of the present invention to provide a bobbin case of a rotary shuttle device for a sewing machine, in which the under thread can be stably supplied and the sewing machine can be silently operated, thereby increasing the quality of sewn products.
It is yet another object of the present invention to provide a bobbin case of a rotary shuttle device for a sewing machine, which is capable of facilely inserting one end of the under thread wound on the bobbin into the discharging hole.
To accomplish the above objects and advantages, there is provided a bobbin case of a rotary shuttle device for a sewing machine, in which a bobbin for winding an under thread is rotatably disposed, comprising a main body integrally provided with a body, and a side portion which is bent downward at a side of the body to have a thick portion at which a fixing hole and adjusting hole is formed and a think portion at which a first and second supporting portion and a supporting piece for supporting and guiding the under thread are formed, the first and second supporting portions being divided by a boundary portion which is formed with a discharging hole for discharging the under thread pulled out of a bobbin from an inner portion of the side portion to an outside; and a guide member formed with a coupling hole and a controlling hole which is corresponding to the fixing hole and the adjusting hole and through which a fastening bolt and a controlling bolt are releasably screwed, wherein one end of the guide member is also formed with a first fixing piece and a second fixing piece which are respectively fixedly inserted into the first and second supporting hole formed at the side portion of the main body, and the second fixing piece forms a path, through which the under thread is passed, together with the supporting piece.